Printed Circuit Cable Assemblies (PCCAs) for magnetic disc drives incorporate connection traces for micro-actuators. Manufacturers have added filter capacitors whose capacitances are as low as 100 picofarads to the connection traces in PCCAs. The presence of these capacitors must be detected during the PCCA assembly process.
Detection and measurement of capacitive devices is normally performed by applying an alternating current signal to the capacitor being tested and measuring the phase difference between the applied voltage and the current drawn. This method is suboptimal for lower-capacitance capacitors because the difference in current caused by these capacitors is too small to be easily detected.